Traffic fatalities: does income inequality create an externality?

Responsible for 20 million severe injuries and/or deaths annually, few epidemics receive less attention than traffic accidents. Going beyond confirming an inverted U-shaped relationship between mean income and fatalities, we show theoretically that income inequality can positively affect fatalities in two ways. Each operates through heterogeneity between road users, and while the direct effect can be expected to evaporate with rising income, the indirect effect may prove to be an externality in that the relationship remains regardless of the level of income. Our model is supported by evidence from 79 countries between 1970 and 2000.